In 1896, the well-known Kantian idealist Hermann Cohen came forward with extraordinary solemn jubilation in the preface to the 5th edition of the *History of Materialism*, falsified by Fr. Albert Lange. "Theoretical idealism," exclaimed H. Cohen (p. XXVI), "has begun to shake materialism among natural scientists and perhaps will soon defeat it entirely." "Idealism permeates (Durchwirkung) the new physics." "Atomism had to give way to dynamism." "The remarkable turn consists in the fact that the deepening into chemical problems of matter was destined to lead to the principal overcoming of the materialist view of matter. Just as Thales produced the first abstraction by isolating the concept of substance and connected speculative reflections on the electron with it, so the theories of electricity were destined to produce the greatest upheaval in our understanding of matter and, by transforming matter into force, to lead to the victory of idealism" (p. XXIX).

H. Cohen marks the basic philosophical tendencies just as definitively and clearly as J. Ward, without losing himself (as our Machists lose themselves) in petty distinctions of some energetic, symbolic, empiriocritical, empiriomonistic, and similar idealism. Cohen grasps the basic philosophical tendency of that school in physics which is now connected with the names of Mach, Poincaré, and others, correctly characterizing this tendency as idealistic. "The transformation of matter into force" appears here to Cohen as the principal conquest of idealism—precisely as it did for those natural scientists-"spirit-seers" whom I. Dietzgen exposed in 1869. Electricity is declared an ally of idealism because it destroyed the old theory of the structure of matter, decomposed the atom, and revealed new forms of material motion so unlike the old ones, so far still unexplored, unstudied, unusual, "miraculous," that one can slip through an interpretation of nature as non-material (spiritual, mental, psychical) motion. Yesterday's limit to our knowledge of infinitely small particles of matter has vanished—consequently, concludes the idealist philosopher—matter has vanished (and thought remained). Every physicist and every engineer knows that electricity is (material) motion, but no one knows exactly what is moving here—consequently, concludes the idealist philosopher—we can deceive the philosophically uneducated masses with an enticingly "economical" proposal: let us think of motion without matter…

H. Cohen endeavors to recruit the famous physicist Heinrich Hertz as his ally. Hertz is ours, he is a Kantian, he has an a priori assumption! Hertz is ours, he is a Machist, argues the Machist Kleinpeter, because in Hertz there gleams "the same subjectivist view as in Mach concerning the essence of our concepts."[175] This curious dispute about whose Hertz is gives a good example of how idealist philosophers seize upon the slightest error, the slightest lack of clarity in expression on the part of famous natural scientists in order to justify their renewed defense of fideism. In reality, the philosophical introduction of H. Hertz to his *Mechanics*[176] shows the usual viewpoint of a natural scientist frightened by professorial howling against the "metaphysics" of materialism, but wholly unable to overcome the spontaneous conviction in the reality of the external world. This Kleinpeter himself admits, on the one hand throwing into the masses utterly mendacious popular pamphlets on the theory of knowledge of natural science, in which Mach figures alongside Hertz—on the other hand, in specialized philosophical articles admitting that "Hertz, in contrast to Mach and Pearson, still holds the prejudice concerning the possibility of mechanically explaining all of physics,"[177] that he preserves the concept of the thing-in-itself and "the usual viewpoint of physicists," that Hertz "still clung to the existence of the world in itself,"[178] etc.

It is interesting to note Hertz's view of energetics. "If we," he wrote, "ask why precisely contemporary physics loves to use the energetic mode of expression in its reasoning, the answer will be this: because in this way it is most convenient to avoid speaking about things concerning which we know very little… Of course, we are all convinced that ponderable matter consists of atoms; concerning their magnitude and their motions in certain cases we have quite definite conceptions. But the form of atoms, their cohesion, their motions in most cases are completely hidden from us… Therefore, our conceptions of atoms represent an important and interesting goal of further investigations, by no means being especially suitable to serve as a firm foundation for mathematical theories" (vol. I, p. III, 21). Hertz awaited from further study of the ether the clarification of "the essence of old matter, its inertia and force of gravitation" (I, 354).

From this it is evident that it does not even occur to Hertz that a non-materialist view of energy is possible. For philosophers, energetics served as an occasion for flight from materialism to idealism. The natural scientist regards energetics as a convenient mode of expounding the laws of material motion at a time when physicists have, so to speak, departed from the atom but not yet arrived at the electron. This time still continues to a considerable degree: one hypothesis is replaced by another; concerning the positive electron nothing is known at all; only three months ago (June 22, 1908), Jean Becquerel reported to the French Academy of Sciences that he had succeeded in finding this "new constituent part of matter" (*Comptes rendus des séances de l'Académie des Sciences*, p. 1311[179]). How then not to take advantage of idealist philosophy by such a favorable circumstance, that "matter" is still only being "sought" by the human mind—consequently, it is nothing more than a "symbol," etc.

Another German idealist, of a far more reactionary shade than Cohen, Eduard von Hartmann, devoted an entire book to "The Worldview of Modern Physics" (*Die Weltanschauung der modernen Physik*, Lpz., 1902). We are not concerned, of course, with the author's special arguments about that variety of idealism which he defends. We need only point out that this idealist too records the same phenomena which were recorded by Rey, Ward, and Cohen. "Contemporary physics grew on realist soil," says E. Hartmann, "and only the neo-Kantian and agnostic currents of our epoch have led to the final results of physics being interpreted in an idealist sense" (218). Three gnoseo­logical systems, in the opinion of E. Hartmann, underlie modern physics: hylokinet­ics (from the Greek words hyle = matter and kinesis = motion—i.e., the recognition of physical phenomena as movement of matter), energetics, and dynamism (i.e., the recognition of force without substance). It is understandable that the idealist Hartmann defends "dynamism," derives from this that the laws of nature are world-thought, in short, "substitutes" the psychical under physical nature. But he is forced to admit that hylokinetics has the majority of physicists on its side, that this system is "most frequently employed" (190), that a serious deficiency of it consists in "materialism and atheism threatening pure hylokinetics" (189). The author regards energetics quite correctly as an intermediate system and calls it agnosticism (136). Of course, it is "an ally of pure dynamism because it eliminates substance" (p. VI, p. 192), but its agnosticism does not please Hartmann as a certain "Anglophilia" contradicting the genuine idealism of a truly German reactionary.

It is extremely instructive to see how this party-irreconcilable idealist (unprincipled people in philosophy are just as hopeless dunces as in politics) explains to physicists what exactly it means to proceed along one or another gnoseo­logical line. "The most insignificant part of those physicists who follow this fashion," writes Hartmann concerning the idealist interpretation of the final results of physics, "are fully aware of all the significance and all the consequences of such an interpretation. They have not noticed that physics with its particular laws maintained independent significance only insofar as physicists, despite their idealism, held to realist fundamental premises, namely: the existence of things-in-themselves, the real changeability of them in time, real causality… Only under these realist premises (the transcendental significance of causality, time, space with three dimensions), i.e., only under the condition that nature, of whose laws physicists speak, coincides with the realm of things-in-themselves… can one speak of laws of nature in distinction from psychological laws. Only in the case where the laws of nature act in a realm independent of our thinking can they serve as an explanation of the fact that logically necessary conclusions from our images turn out to be images of naturally-historically-necessary results of that unknown which these images reflect or symbolize in our consciousness" (pp. 218–219).

Hartmann rightly senses that the idealism of new physics is precisely a fashion, not a serious philosophical turn away from natural-historical materialism, and he rightly explains therefore to physicists that in order to transform "fashion" into a consistent, integral philosophical idealism one must radically refashion the doctrine concerning the objective reality of time, space, causality, and the laws of nature. One cannot only regard atoms, electrons, ether as a simple symbol, a simple "working hypothesis"—one must declare "working hypothesis" also time, and space, and the laws of nature, and the entire external world. Either materialism or universal substitution of the psychical under the entire physical nature; mixing these two crafts is the occupation of countless hunters, but Bogdanov and I are not of their number.

Among German physicists, Ludwig Boltzmann, who died in 1906, systematically struggled against the Machist tendency. We have already indicated that against "infatuation with new gnoseo­logical dogmas" he opposed the simple and clear reduction of Machism to solipsism (see above, Ch. I, § 6). Boltzmann, of course, is afraid to call himself a materialist and even specifically stipulates that he is by no means against the existence of God.[180] But his theory of knowledge is essentially materialist, and expresses it—as Z. Günther, the historian of natural science in the 19th century, admits[181]—the opinion of the majority of natural scientists. "We cognize the existence of all things from those impressions," says L. Boltzmann, "which they produce on our senses" (p. 29). Theory is "an image" (or: copy) of nature, of the external world (77). To those who say that matter is only a complex of sensuous sensations, Boltzmann points out that then other people too are only sensations of the speaker (168). These "ideologists," as Boltzmann sometimes says instead of: philosophical idealists, draw for us a "subjective picture of the world" (176), while the author prefers "the simpler objective picture of the world." "The idealist compares the assertion that matter exists in the same way as our sensations with the opinion of a child that a beaten stone experiences pain. The realist compares that opinion, according to which one cannot imagine how the psychical arises from the material or even from the play of atoms, with the opinion of an uneducated man who asserts that the sun cannot be 20 million miles from the earth because he cannot imagine this" (186). Boltzmann does not renounce the ideal of science to represent spirit and will as "complex actions of particles of matter" (396).

Against Ostwald's energetics L. Boltzmann polemicized repeatedly from the standpoint of a physicist, proving that the formulas of kinetic energy (one-half mass multiplied by the square of velocity) Ostwald can neither refute nor eliminate and that he moves in a vicious circle, deriving at first energy from mass (accepting the formula of kinetic energy), and then defining mass as energy (pp. 112, 139). In this connection I recall Bogdanov's paraphrase of Mach in the third book of *Empiriomonism*. "In science," writes Bogdanov, citing Mach's *Mechanics*, "the concept of matter is reduced to the coefficient of mass appearing in the equations of mechanics, and this latter upon precise analysis turns out to be the inverse magnitude of acceleration in the interaction of two physical complexes—bodies" (p. 146). It is understandable that if one takes some body as a unit, the motion (mechanical) of all other bodies can be expressed by a simple ratio of acceleration. But then "bodies" (i.e., matter) do not thereby disappear at all, do not cease to exist independently of our consciousness. When the entire world is reduced to the motion of electrons, from all equations one will be able to eliminate the electron precisely because it will be presupposed everywhere, and the relations of groups or aggregates of electrons will be reduced to their mutual acceleration—if the forms of motion were as simple as in mechanics.

In struggling against the "phenomenological" physics of Mach and Co., Boltzmann asserted that "those who think to eliminate atomistics by means of differential equations do not see the forest for the trees" (144). "If one does not delude oneself about the significance of differential equations, there cannot be doubt that the picture of the world (by means of differential equations) will necessarily still be atomistic, a picture of how, according to certain rules, vast quantities of things arranged in space with three dimensions will change in time. These things can, of course, be identical or different, unchanging or changeable," etc. (156). "It is perfectly obvious that phenomenological physics only clothes itself in the garment of differential equations," says Boltzmann in 1899 in a speech at the Munich congress of natural scientists, "but in reality it proceeds equally from atom-like individual beings (Einzelwesen). And since these beings must be conceived as possessing now one, now another properties for different groups of phenomena, there will soon appear the need for a simpler and more uniform atomistics" (223). "The doctrine of electrons is developing precisely into an atomistic theory of all phenomena of electricity" (357). The unity of nature reveals itself in the "striking analogy" of differential equations relating to different domains of phenomena. "With those very same equations one can solve questions of hydrodynamics and express the theory of potentials. The theory of vortices in liquids and the theory of friction of gases (Gasreibung) reveal striking analogy with the theory of electromagnetism, etc." (7). People recognizing the "theory of universal substitution" cannot by any means escape the question: who then so uniformly guessed to "substitute" physical nature.

As if in answer to people who dismiss "the old-school physicist," Boltzmann recounts in detail how some specialists in "physical chemistry" take a gnoseo­logical standpoint opposed to Machism. The author of "one of the best," according to Boltzmann, comprehensive works of 1903, Vaubel, "takes a decidedly hostile position toward the so frequently lauded phenomenological physics" (381). "He strives to form as concrete and clear a conception as possible of the nature of atoms and molecules and of the forces acting between them. This conception he brings into accord with the most recent experiments in this field" (ions, electrons, radium, the Zeeman effect, etc.). "The author strictly holds to the dualism of matter and energy,[182] separately expounding the law of conservation of matter and the law of conservation of energy. With respect to matter the author again holds to the dualism of ponderable matter and ether, but the latter he regards in the strictest sense as material" (381). In the second volume of his work (the theory of electricity), the author "from the very beginning takes the standpoint that electrical phenomena are caused by the interaction and motion of atom-like individuals, namely electrons" (383). Consequently, with respect to Germany too, there is confirmed what, with respect to England, the spiritualist J. Ward acknowledged, namely: that physicists of the realist school systematize the facts and discoveries of recent years no less successfully than physicists of the symbolist school, and that the essential difference consists "only" in the gnoseo­logical standpoint.[183]